Automotive paint over West Systems epoxy?

Discussion in 'Materials' started by Ram4x4, Oct 10, 2015.

  1. Ram4x4
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    Ram4x4 Junior Member

    Hello,

    I race a C-class hydroplane in American Power Boat Association sanctioned races.

    My boat is built of thin marine ply and coated with West Systems epoxy w/207 hardener (no blush).

    Can I paint right over the epoxy with automotive enamel, or should I prime it first?

    Thanks!
     
  2. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    There's no such thing as "blush free", even with the blush free formulations, though some are much lower in blush and you can employ environmental conditions that resist blush to a large degree. So, unless you've coated your boat in a nearly sterile, climate controlled environment, then consider the potential for blush, as quite possible. Simply put, wash the surface with warm water and a touch of dish detergent, then rinse and dry it, then move onto scuffing it up, for subsequent coatings.

    As a rule, most paints can go directly over epoxy, but this isn't my recommendation, especially if you'll be using an alkyd. Some alkyds can react badly with epoxy, so the usual recommendation is to prime, then paint, just to insure you have a solid "tie coat" between the substrate and the topcoat. In fact, I use an epoxy primer. Using a primer also permits you to fine tune the finish, by offering some bulk to block it smooth, before the finish coats go down.
     
  3. SukiSolo
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    SukiSolo Senior Member

    I agree with PAR, you will benefit from abrading the epoxy and using a primer/filler to really get it smooth. However on small craft I have used both epoxy 2k primers and 2k acrylic/polyurethane (automotive) hi build primers without a problem. The main problem is simply that the paint is heavy so cutting back for real fairness is useful. I've used stuff like PPG Kobe 5:1 for example.
    If you are after say a white finish I'd probably put a thin undercoat on next then top coat.

    There may be problems when you get over 6 to 7 meters in length with automotive paints as they are generally a fraction less 'elastic' so expansion contraction issues may require a additive allowing more flex. However on shorter stuff I've not had a problem. The top coat will buff to perfection and although you will get a little epoxy sink over say the first two years even this can be cut and rebuffed to perfect smoothness.

    My preference is to use all 2k systems over epoxy as it is pretty stable and allows a good durable finish to be applied. Not cheap but tends to payback in terms of service life. I would not recommend cellulose systems at all....
     
  4. Ram4x4
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    Ram4x4 Junior Member

    Yikes!

    Ok, thanks guys, a bit more technical than I expected. I'm not a paint finish pro by any means and I'm really looking to do this is cheaply as I can. It's not necessary to be show quality and if it holds up for a year or so, that'd be great (it'll get banged up during racing anyway).

    I was looking at going with something like this:

    https://www.paintforcars.com/enamel_paint_kits.html

    with a clear coat on it.

    Time, sandpaper and a buffer I have, big $$$ to paint this thing I don't have.

    I even considered plasti dip at one point, but I don't think it would hold up, especially on the bottom.
     
  5. PAR
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    PAR Yacht Designer/Builder

    These single stage acrylics don't need a clear coat (which makes them a two stage system). Simply add the appropriate hardener and it'll gloss up fairly well. It will not be as deep and rich as the two stage jobs, but close enough for the budget minded. These paints aren't like the two stage LPU's or acrylic urethanes, which can be sanded in an hour and buffed within some hours. Typically with these modified enamels, you'll have to wait 24 hours to wet sand the stipple, then a week or more to buff it out. They are fairly hard, have good gloss retention and durability, but aren't quite as good as the two stages systems.
     
  6. Ram4x4
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    Ram4x4 Junior Member

    So it'd be ok to shoot that acrylic right over prepped epoxy?

    Would shooting clear over it give it a better appearance?

    I don't mind the small extra cost of some clear in addition to the paint in this case.

    I can do a few coats of the paint, or lesser coats of paint and a couple clear...it's still several layers of paint but if the clear will make it look a little better then that's ok too.

    As for urethanes, I've been told that unless I have an air helmet set up not to use them with a respirator, supposedly very, very bad thing to do?
     
  7. SukiSolo
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    SukiSolo Senior Member

    It is not the fact it is urethane based, it is the two pack hardeners for both acrylics/polyurethanes and blends of that contain isocyanates. These are known carcinogens so spraying with no mask is a bad idea. Brush or roller and there are minimal or no isocyanates in the vapour. Commercially you require an air fed mask and proper extraction, water bath etc etc. However for a brief one off, spraying in a well ventilated space with a good correct filter mask you could get away with it....;)
     
  8. PAR
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    PAR Yacht Designer/Builder

    Adding clear over this type of enamel isn't going to help much, though you'll gain a little depth, you'll also expose the finish to more potential issues (stipple, bugs, dust, etc.). These single stage enamels are intend to shoot and lay down nice, right out of the can (appropriate mix of course). The idea is to offer the garage builder a chance, with a modest priced product with the ease of a single stage, yet many of the looks of a two stage.

    Even though you probably (no guarantees with enamels) can squirt this enamel over epoxy, you're still much better off with a primer coat, if for no other reason than to offer something to truly level and smooth the surface. As I previously mentioned, some enamels can react poorly, directly over epoxy and without previous tests on this paint/epoxy combination, it's a crapshoot as to if you'll have problems, so primer is the safe, reliable bet. It's also a whole lot easier to level primer than epoxy.

    Simply put, since you're not a pro and are looking to spank this puppy relatively cheaply, just use a good primer and squirt the single stage over it. You can always go back a apply a clear if you think your prep deserves it, but be careful what you ask for, as a really glossy finish will show off every single spot, you should have put more time into, during the prep stages.
     
  9. Ram4x4
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    Ram4x4 Junior Member

  10. Dave T
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    Dave T Senior Member

    I recently repainted the bottom of my homemade wooden boat using Menards marine top coat primer and paint. The paint seems to have held up well after one summer of use. This is a trailer boat that is usually in the water for three days most weekends and was in the water for 10 days during vacation. I considered trying swimming pool paint in particular insul-X-1023 Waterborne Acrylic Pool paint. Since swimming pools are usually filled for a season at time it seems this would have to be pretty waterproof and resistant to the chemicals used for disinfection. The cost is pretty reasonable at $94.54 for two gallons. Does anybody know anything about this type of paint or had any experience with it.

    Dave T :confused:
     
  11. PAR
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    PAR Yacht Designer/Builder

    Auto-Air paints have been around for a while, initially developed for sign and airbrush painters, now seeing some use as base coats under urethane clears. These waterborne products are very different than automotive style of paints and rival the cheaper LPU's in cost. Ram4x4, you're going to have more trouble with this type of paint than an enamel or single stage urethane. You should stick with what you know and/or have equipment for. As an example, if you have a regular automotive HVLP gravity feed setup, you'll need new tips (or you'll need to drill them out), to squirt these waterborne paints. This paint also needs to be post cured for best results, before the clear goes down. So, do you have a big oven? How about clean air, isolating drying fans? This said, I've heard they are vibrant in color and easier to apply than the LPU systems, but they take some "getting used to".

    What are you looking for Ram4x4? You seem to be jumping around, possibly searching for the best, reasonably priced paint system, but there's no such thing, just the ones you "get along with" best. Basicly, if you have a comfort level, you're best results with be with that system. If you have no real experience, then stick with the simpler systems, without special reducers, drying and wetting agents, etc. The more elements to the paint system, the more potential exposure to problems. For example, if you can squirt lacquer, than this is about as easy a paint you can shoot. No, it's not as durable and other stuff, but it's not going to cost much, a trained monkey can apply it and you can rub it out to a nice finish, without the need for a environmentally controlled paint and drying booth, not to mention air supply equipment.

    Have often considered that type of paint Dave, but haven't been willing to try it on one of my boats, let alone a client's.
     
  12. Ram4x4
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    Ram4x4 Junior Member

    I don't know what I want :)

    I want to paint my hydro with something that won't break the bank, but be as tough as possible and look good.

    I don't have any spray guns or anything yet. I have a compressor and that's about it.

    I do have experience using an airbrush on t-shirts years ago, and I can do body prep work. I just never had to paint the cars and never concerned myself with all the various types of paint systems.

    I understand what 1K, 2K and single and 2 stage is. I just don't know which of those would be best for my situation, especially considering I've never had to prep and spray a boat.

    If it helps, I plan to get and use that purple spray gun that Harbor Freight sells. I know, it's not a Sata, but like I said, sandpaper and time I do have.

    There's a guy in our group that actually painted his hydro with rattle cans, cleared it with rattle cans and wet sanded and buffed it and dang if it don't look really good...the problem is, the paint dings really easy.

    I've done similar on small things and I can get an incredible shine on it.

    I also am a woodworker as a hobbyist (over 25 years doing that) and I deal with clear finishes on wood. I have some sandpaper that goes to 12,000 grit. Rattle can lacquer rubbed out to 12,000 grit is like glass, even before polishing it.

    I just want to do it a step better and have paint that is durable. I'm confident I can get a good shine on it.

    I've toyed with the idea of using an airbrush and doing some small effects (like the water bubble trick), or throwing in some color flip pearls...but that sort of thing gets pricey fast.

    At this point, I'll settle for a nice solid color that is as durable as I can get on a budget and play with fancy later. I do plan to experiment with it at a later date (when I can spend the money on good equipment and paint). I just need a good paint job on it for the start of the season which begins in late April/early May. The problem is that here in north western PA it ain't very warm until the last second before race season, and my barn isn't heated, so I can't paint until then and will have a short window to get it done.

    Plus, I'm just trying to learn too :)
     

  13. PAR
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    PAR Yacht Designer/Builder

    Again, given your experience level, lack of tools, etc., you're better off with a single stage polyurethane or modified alkyd. These will be the easiest and cheapest to apply. These paints will dry without special conditions and controls. The drawback is they're not as tough as the $300 a gallon stuff.

    Harbor Freight guns are a waste of time, unless you enjoy spit and sputter. Hell, a Wagner hand shaker unit will do as good a job.

    One trick to get a fantastic paint job is to thin the paint about 40% and apply many coats. You can use a brush and tip it off, but you don't have to. Let it run and sag. You'll wet sand these blemishes out after each pass. It takes 6 or more coats, to bulk the film thickness to that of 2 good ones, but you can be a real slob about applying them, knowing you just knock them flat after each pass. This just requires labor, no real equipment and the results are as anal as you want.

    As soon as you step up to the acrylic urethanes and LPU's, the application difficulty rises up considerably. You don't just need a compressor, but you need a good one, with the CFM a production gun requires and the 2 HP 15 gallon tank Craftsman unit most homeowners have, just will not do. My compressor is a small one at 5 HP single stage, 60 gallon, generating 18.5 CFM at 90 PSI. It's about as small as you want if you're running air tools, though occasional spraying can use a smaller one, say 14 - 15 CFM. Then you'll want a drier, oil/water separator, particulate and carbon filter, etc. all for just the compressor.

    It more than just the cost of these fancier paints too. They usually require special reducers, driers and other chemicals. These things add up quickly, making a $100 a gallon paint, a $200+ an applied gallon paint job.

    If you want the paint job to last, insure good prep (with primer), take care of it, don't beat it up too bad, keep it clean, dry and out of the direct sun. On the other hand, you could run it down to the local Maaco or Earl Scheib and have a $250 "Presidential Special" squirted on her, for less than the paint and solvents you'd need to do it yourself. Yeah, you'll have to buff the crap out of it when it comes back, but . . .
     
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